Our invention relates to a method of makeready for a web printing press of the type having a print station designed for interchangeable use of different size printing cylinders, and at least one other processing station for performing such an operation as perforation on the printed web, both print and processing stations being driven by a common drive shaft having a clutch disengageable to permit the print station to be driven independently of the processing station. More specifically, our invention pertains to a method of reconnecting, after declutching, the sections of the common drive shaft with the print and processing stations in phase with each other.
The method of our invention finds a typical application in web printing presses of the type used in the manufacture of business forms, wherein the web travels through a succession of stations such as those for printing, perforating, numbering, punching, slitting, and zigzag folding. An example of this type of printing apparatus is extensively discussed in U.S. Pat. No. 4,177,730 issued Dec. 11, 1979, to Schriber et al. and entitled "Method and Apparatus for Web Printing".
In the web printing press of the type under consideration, the need arises for driving only the print station, as for cleaning the ink or for spreading a new ink over the entire surfaces of the printing cylinders. The continued feeding of the web during such independent operation of the print station would result in a waste of paper. Cutting the web is also objectionable as the web must again be threaded through the press with the consumption of a considerable length of time.
We are aware of a conventional solution to this problem, involving the use of two clutches on the common drive shaft, one between the web unwind station and the print station and the other between the print station and the next processing station. The clutches are both disengaged for driving only the print station by a motor coupled to the drive shaft section between the clutches. This solution is satisfactory for printing presses employing fixed sizes of printing cylinders only. The circumference of the plate cylinder and the traveling distance of the web per revolution of the drive shaft are both constant in such presses. Thus the mating members of the clutch between the print station and the subsequent processing station may be so constructed as to interengage only in predetermined relative angular positions where the stations are in phase.
The above solution is unsatisfactory, however, when applied to those presses which are adated for interchangeable use of several different size plate cylinders. While the circumference of each plate cylinder differs, the traveling distance of the web per revolution of the drive shaft remains the same. Consequently, once the drive shaft sections are declutched, and a different size plate cylinder installed at the print station, one of the drive shaft sections must be turned a definite number of revolutions before being reconnected to the other section with the print and later processing stations in phase. Suppose for instance that a plate cylinder with a circumference of twelve inches has now been installed, and that the web is fed eleven inches per revolution of the drive shaft. Then, once the clutch between the print station and the next processing station is disengaged, the drive shaft section for the print station must be turned twelve revolutions from its initial angular position before being reconnected in phase to the drive shaft section for the processing station.
Conventionally, therefore, a jaw clutch has been employed between the drive shaft section for the print station and that for the subsequent processing station, in order to allow these drive shaft sections in any of several predetermined different angular positions with respect to each other. With the jaw clutch reengaged after the mounting of each new different diameter plate cylinder at the print station, the printing press has been set into operation for printing and subsequently perforating or otherwise processing the web. Then the printed and processed web has been inspected to determine the extent to which the print station and processing station are out of phase. Then the jaw clutch has been disengaged and, after readjusting the relative angular positions of the drive shaft sections as required, reengaged. Thus the conventional phasing operation after the installation of each different size plate cylinder has been very troublesome, time consuming, and has further involved a considerable waste of web.